I have recently bought a 1998 GS500E and after a fair amount of tinkering I have it running on both cylinders but it has an intermittent rattle.  I recenlty left it ticking over to get it warm and the noise seemed to stop.  But when I revved it the noise came back and stayed.  That's how I have left it.
My guess is a sticking valve but I've never experienced this before and not sure what to look for.  any clues.  Obviously it increases with revs and seems worse or more regular when hot.
The only other though I had was the rev counter drive as that doesn't work.
Oil pressure seems fine and all cams and valve clearances have been checked.

Did you check for cam end play? On some motors there was a problem with that. Evidently, there are shims (washers) that need to be in put in to fix the noise.

I'll check that, but this is a real knock from the top end.  Doesn't sound like a big end or little end.  Also timing chain and adjuster all seem tight and tensioner working.

Thanks

These bikes are plagued by "cam end float".  As the engine heats and the cam journals expand the cam is allowed to move side to side slightly and it creates a rattle.  It would be as you describe, faster with RPM and noiser as engine comes up to temp.

I wouldn't worry about it, necessarily, unless it's making an unholy racket.

These bikes are also pretty well known for "spark knock" if you're bike is making a clicking noise, only under load [speeding up, going up a hill] but isn't making noise at sustained speed, or idle. you've got the spark knock. there's a few things you can do, one that worked for me was going up JUST ONE. grade on the gas pump.


and the reason for these bikes having the spark knock has to do with the internal temperature of the engine, being air cooled and all.

Copied from old post of mine:

Knocks only when hot, only at idle, and stops knocking when engine is speeded up to a fast idle or faster?  If so it's probably the cam knock if your GSF is older than 05-06.  Suzuki finally fixed it with a camshaft change after that.

I had it on my 97 bought new that I rode from 99-03 when it was totaled and replaced with my current 02 model which also had it at first and it has over 100k miles on it now.  After first hearing and diagnosing it on the 97 it went away around 50k miles after I changed from 15W-50 Mobil synthetic to 15W-40 Rotella T dino juice.  Changed the 02 to the same Rotella T not long after I bought it used with only 4k niles on it and cam knock went away around then I think, it was a long time ago now.  Can't say for sure oil change fixed it but it's long gone and it's harmless anyway if that's what you have.

Copied from another old post of mine concerning gas knock aka spark knock:

My 97 GS progressed from regular to mid grade to premium gasoline to prevent gas knock in hot weather as the miles and carbon built up same as the 4 Hondas I used 20W-50 in summers did previous to the GSs.

When I switched from the 15W-50 to the 15W-40 in the 97 I went back to regular gas year round without gas knock and have used regular gas all my 100k miles on the 02 also w/o knock.

The GSs run cooler on a xxW-40 oil than on a xxW-50 oil and your doing it no favor using the heavier oil in hot weather unless oil consumption is real bad.  Besides lubricating the engine the oil also provides cooling by carrying heat away from the head to the sump.  This cooling flow is reduced with the heavier oils.

The GS5 does not have a quiet top end at the best of times but there is an easy test to determine if the noise is cam float.

Just lean the bike hard over to the left then the right and see what happens. 

Thanks for all that info.  As it's not road worthy I can't tell what it does under load.  I have a fair amount of knowledge and experience in engines but each engine has it's own unique problems.  I still think I have something a bit more serious than cam floating.  I did buy it as a bike that needed a new top end.  But I like to figure things out for myself ! Can anyone confirm if the valves can hit the piston ? Just to eliminate one theory of a bent valve.  Although how it would bend even if it does hit I don't know. 
I understand it possibly ran low on oil at some point.  I still don't think it's a big or small end though.

Quote from: manwithtool on July 20, 2017, 07:29:30 AM....................Can anyone confirm if the valves can hit the piston ? Just to eliminate one theory of a bent valve.  Although how it would bend even if it does hit I don't know.................

I don't believe the valves can hit the piston but I do know they can hit each other if one sticks open.  My 02 had a tight bucket and one freezing cold morning an exhaust valve stuck open while cranking to start and was hit by the intake valve and it broke off.  The intake valve had a knick to show it and the piston was unmarked.

Update,  I removed the engine, removed the head and took the valves out.  I couldn't see anything wrong.  The only thing that looked a little wrong was the rev counter drive which seemed to float back and forward about 5 mm.  Could this have been my tappety noise that comes and goes ?

I installed my new head and re installed the engine after re setting the valve clearances.  Started the bike up and I now have a consistent tappet knock.  I rechecked the valve clearances and a couple were too large.  re set them and tried again....same knock.  I rechecked the valve timing and it was one tooth out.  Re set it and started it again.  Same knock.  Really sounds like the top end and as it's now a consistent knock rather than the previous sound I do feel like the problem is top end not a little end or big end.

I removed the rev counter drive completely and blocked the hole.  Really does sound like one valve making the knock...similar noise to when I started it once without one of the shims in place.  Pretty terrible sound but now consistent and in time with the valves I think.

Have you checked you cam shaft end play ? Anything over 1/4mm and it will clack. Over 1/2 mm and it will clack regularly at almost all rpm's.
Cool.
Buddha.

You've changed the head and still have the noise, maybe time to look elsewhere.  Had a loose starter clutch myself and was sure the knock was coming from one of the cylinders at first.  When the noise progressed I finally found it.

Camshaft seems ok.  I'll check the starter motor clutch though.  good job my time is free otherwise I'd be broke !

Cam shaft with 1mm of end float is "OK" too.
The thinnest shim they sell is 1.1mm. By the time you get to .5mm you will absolutely go nuts.
Cool.
Buddha.

lol no doubt.
Aaron

I've fixed cam shaft end play float on a 1991 by shimming it with some hardened steel plate that was hole punched, and went on the very end of the cam next to the cam boots. last I heard he's put 15k on it. still not noisy yet. I forget how much "play" there was. but it was pretty noticeable before it. now it just sounds like a GS.  it's an idea.. but 100% used hardened materiel. I think soft would get chewed up and possibly break, sending bits into the engine being so thin an all. better safe then sorry.

He he, on my 89 I welded up aluminum onto the side of the intake cam journals and machined them down to their original size +.2mm.
Exhaust journals I didn't touch, cos it was less than .2mm. Intake was over .4mm.
Cool.
Buddha.

Quote from: The Buddha on August 30, 2017, 06:47:50 PM
He he, on my 89 I welded up aluminum onto the side of the intake cam journals and machined them down to their original size +.2mm.
Exhaust journals I didn't touch, cos it was less than .2mm. Intake was over .4mm.
Cool.
Buddha.

That's a good idea, and probably what I would of done, if I had access to a mill and some TIG machinery at the time.

Now if we can collectively come up with a part to replace the OEM crank triggers.... 

Quick update,

There was some end float in the cam, but not enough to get another shim in.  So I made up a copper washer to take it up.  We did notice the Exhaust cam drive sprocket seemed to "wobble " a little and depending on the position of the cam the cam would have some endfloat and in other positions none.  This would point to a bent cam shaft possibly...BUT, I think it's more likely to be the cam pushin on the valve that holds it in place.  AND this is a different cam than the original head that had a knock.

So although I think this knock is slightly different to the original noise I had.  Changing head including cams and valves has not made the problem go away.  It seems to be a definite knock from the left cylinder Ex valve.

Anyway, I've given up and bought a second hand engine so will be cleaning that up and servicing it ready to install at some point.

Anyone want an engine is pretty good condition apart form a funny knock ??